1. Field of the Invention
The present invention relates to a triple view imaging apparatus suitable for use with optical microscopes and more particularly to the triple view imaging apparatus for measuring two-dimensional distribution of various components or properties in a sample.
2. Description of the Related Art
There have been proposed conventional triple view imaging apparatuses as shown in FIGS. 1 and 2.
The conventional triple view imaging apparatus shown in FIG. 1 includes an optical system 2 which confronts a sample 1, a video camera 3 installed to receive light which has emitted or reflected from the sample 1 and passed through the optical system 2, and an image processor 4 which is equipped with a built-in computing device (not shown in the drawing).
The optical system 2 includes a first band-pass filter 2a and a second band-pass filter 2b. The optical system 2 operates to switch positions of the first and second band-pass filters 2a and 2b so that the light from the sample 1 passes through either the band-pass filter 2a or 2b. The first band-pass filter 2a selectively transmits light with a certain wavelength band (which will be referred to as a "first wavelength band," hereinafter), and the second bandpass filter 2b selectively transmits light with another wavelength band which is different from the first wavelength band (which will be referred to as a "second wavelength band," hereinafter) Therefore, by switching the positions . of the band-pass filters 2a and 2b, the optical system 2 changes the wavelength band of the optical image of the sample 1 to be inputted to the video camera 3. (The optical image of the sample 1 with the first wavelength band obtained through the first band-pass filter 2a will be referred to as an "optical image a," and the optical image of the sample 1 with the second wavelength band obtained through the second band-pass filter 2b will be referred to as a "optical image b.")
The video camera 3 receives the optical images of the sample and outputs image signals representing the optical images. More specifically to say, when the video camera 3 receives the optical image a from the band-pass filter 2a, it outputs a first image signal representing the optical image a. When the video camera receives the optical image b from the band-pass filter 2b, it outputs a second image signal representing the optical image b. The first and second image signals thus output from the video camera 3 are inputted to the image processor 4 successively. The image processor 4 converts the optical images a and b into two sets of image data (which will be referred to as "first and second image data" hereinafter), respectively The computing device in the image processor 4 calculates with these two sets of image data the two-dimensional quantitative distribution of components in the sample 1.
However, there has been known a problem in that this conventional triple view imaging apparatus can at one time pick up only a single optical image transmitted by either the first or second band-pass filter 2a or 2b. More specifically, the video camera 3 first picks up the optical image a of the sample transmitted by the first band-pass filter 2a. The image processor 4 temporarily stores the first image data in a frame memory. Next, the optical system 2 switches to the second band-pass filter 2b. The video camera 3 picks up the optical image b of the sample transmitted by the second band-pass filter 2b and accordingly the image processor 4 obtains the second image data. Then, the computing device retrieves, and performs calculations on, these two sets of image data to obtain the quantitative distribution of the components in the sample 1. In the conventional triple view imaging apparatus having the above-described structure, a time lag is created between when the optical image a is transmitted through the first band-pass filter 2a and when the optical image b is transmitted through the second band-pass filter 2b. Movements or transformations in the sample 1 that will possibly occur during this time lag may degrade measurement precision. Further, this time lag will frustrate any attempt to measure such temporal movements or transformations with this conventional triple view imaging apparatus.
To solve this problem, another type of triple view imaging apparatus has been proposed by Kazuhiko Tamura et al., in their article "SIMULTANEOUS MEASUREMENT OF CYTOSOLIC FREE CALCIUM CONCENTRATION AND CELL CIRCUMFERENCE DURING CONTRACTION, BOTH IN A SINGLE RAT CARDIOMUSCULAR CELL, BY DIGITAL IMAGING MICROSCOPY WITH INDO-1" published in Biochemical and Biophysical Research Communications Vol. 162, No. 3 (1989): 926-932. This type of triple view imaging apparatus is schematically shown in FIG. 2 and allows picking up of the optical images a and b from the same sample 1 simultaneously at two different wavelength bands. This triple view imaging apparatus includes a dichroic mirror 5 which confronts the sample 1, a first band-pass filter 2a, a second band pass filter 2b, a first video camera 3a, a second video camera 3b, and an image processor 4 equipped with a built-in computing device (not shown in the drawing). As in the previous conventional triple view imaging apparatus, the first band-pass filter 2a transmits light with a first wavelength band, and the second band-pass filter 2b transmits light with a second wavelength band which is different from the first wavelength band. The first video camera 3a is installed to receive light (optical image a) which has been emitted or reflected from the sample 1 and transmitted through the first band-pass filter 2a, and the second video camera 3b is installed to receive light (optical image b) which has been emitted or reflected from the sample 1 and transmitted through the second band-pass filter 2b. The first video camera 3a and the second video camera 3b produce image signals Sa and Sb representing the optical images a and b respectively which are then inputted to and processed by the image processor 4. The computing device in the image processor 4 performs calculations on the processed image signals Sa and Sb to quantitatively determine the two-dimensional distribution of the components in the sample 1.
However, this conventional triple view imaging apparatus has created an additional problem in the extra expense required for the two video cameras and, moreover, two systems with image memory and signal processing circuitry for simultaneously processing the image signals Sa and Sb from these two video cameras. There exists a further problem in that image distortion between the two video cameras lowers precision. Troublesome adjustments must be made to correct this image distortion.